The objective of the proposed research is to determine which topological class or classes of ribosomes (free ribosome, ribosomes bound to the endoplasmic reticulum, and perinuclear ribosomes) are involved in the synthesis of specific nuclear proteins and to investigate the mechanism involved in the transport of these proteins from the site of synthesis to their ultimate location in the nucleus. Two non-histone chromosomal proteins (HMG1 and HMG17) will be investigated. Sensitive immunological techniques will be used to detect these proteins among the products of synthesis of each class of ribosomes. By pulse labeling and puromycin release studies, we will attempt to determine whether newly synthesized HMG1 and HMG17 are discharged across a membrane or whether they are, instead, released into the soluble space of the cytoplasm. The newly synthesized proteins will also be compared with the mature proteins to detect postsynthetic modifications which might be involved in the transport process. Finally, we will attempt to define the requirements for transport by use of metabolic inhibitors and by microinjection techniques.